Performance of Hall sensors when used in ground fault protections in MV networks

Ground faults are dominant among disturbances of medium voltage networks and cause numerous problems during their lifetime. Accurate detection and clearing of single phase short-circuits are especially difficult in compensated and/or isolated networks (6-30 kV) with small fault current value. This problem is of particular importance in strip mines due to frequent variations of the network configuration (thus respective change of parameters) under operation. We have found that it is possible to obtain a simple structure of the reliable ground fault protections when applying Hall sensors as measuring elements. In the paper, structure, principle of operation, and investigated results of the overcurrent as well as directional protections are presented and discussed. The investigations were carried out under steady and transient states using special laboratory equipment and verified under real short-circuit conditions in a strip mine. On the basis of the results, the conclusions about the possibility of applications of such protections in practice are formulated.